1. Field of the Invention
The present invention relates to coated triggered start products such as coated triggered start fertilizer products. More particularly, it relates to coated products in particulate form which are structured to provide essentially complete suppression or inhibition of release of active constituents such as fertilizer nutrients from the coated products until release is initiated or triggered by application of a trigger material at a time determined by a user of the products. The invention further relates to processes for producing such coated particulate triggered start products which are effective for preventing premature release of active constituents for a desired period of time, as determined by a user of the products, until release is initiated or triggered by application of a trigger material. Still further, the invention relates to processes for use of the coated particulate triggered start products.
2. Description of Related Art
Controlled release fertilizer (CRF) products which are also termed xe2x80x9cslow releasexe2x80x9d fertilizers have been known heretofore. The known CRF products can be categorized into various groups with one of such groups being coated (or encapsulated) fertilizers. Such coated fertilizers are known to be very effective sources of controlled release nutrients for feeding plants. Specifically, nutrient core materials are released from the coated fertilizers at controlled rates through the fertilizer""s coating resulting in sustained feeding of plants. Thus, a single application of these coated CRF products provides the necessary nutrients for a plant that would require multiple applications of soluble fertilizers.
The functionality of coated CRF products is dependent on the rate of transport of water through the encapsulating or protective coating applied over the granular nutrient core material; and on the rate of release of the core material as a nutrient solution formed when the water entering through the coating contacts the granular core. Thus, the physical nature of the fertilizer core granule itself, the water (vapor) permeability of the coating and the strength of the coating all are factors in achieving the desired release rate of nutrients from CRF products.
One type of coated CRF product in wide use is sulfur-coated fertilizer, such as the fertilizers described in U.S. Pat. Nos. 3,295,950; 3,342,577; 3,576,613; 3,903,333; 4,042,366; 4,636,242; 4,857,098; 4,881,963; 5,219,465; 5,405,426; 5,599,374 and 6,338,746. The release of nutrients from sulfur-coated fertilizers occurs by diffusion through imperfections in the sulfur coating and through coating breakdown resulting from microbial action in the ambient environment. The major advantage of the sulfur-coated fertilizers is their relatively low cost.
Another type of CRF product utilizes polymer coatings such as solvent applied polymer coatings. The polymeric materials applied are either thermosetting resins or thermoplastics. Examples of solvent applied thermosetting resin coated fertilizers, which are currently in use, are disclosed in U.S. Pat. Nos. 3,223,518; 4,657,576 and 4,880,455, whereas examples based on thermoplastics can be found in U.S. Pat. No. 4,019,890. Other polymer coated fertilizers are described in U.S. Pat. Nos. 5,374,292; 5,547,486; 5,652,196 and 5,858,094. Another polymer encapsulated fertilizer that exhibits good controlled release properties is a latex coated granular fertilizer such as the fertilizers disclosed in U.S. Pat. Nos. 4,549,897 and 5,186,732. Both solvent and latex applied polymer coated fertilizers offer important benefits over sulfur-coated products concerning consistency of release rates. The majority of nutrient release is by diffusion through pores in the polymer coating, rather than release through coating imperfections.
The release of nutrient core material from a typical CRF product is initiated when a sufficient amount of water is present in the ambient surroundings for transport through the encapsulating coating into the core. However, this mode of operation presents a commercially significant problem, for example, in regard to the formulation of CRF products suitable for pre-mixing with a substrate such as a growing media. Specifically, growing media such as potting soil, peat moss, coir/pith blends and the like, commonly used in combination with CRF products always contain a significant amount of water (up to 70 wt. %). As a result, it has been a recognized shortcoming of previously available CRF products that, upon storage in growing media, these products have exhibited premature release of their nutrient content resulting in a loss of available nutrients for plant growth when the fertilizer treated growing media are applied after storage. Moreover, the use of such stored CRF-containing growing media is not only inefficient for providing nutrients on a timely basis, but can even be dangerous to the plants since too great a quantity of nutrients may be immediately available when a new plant or seedling is placed in the treated growing media so that the plant or seedling may be damaged.
In order to prevent undesirable water transport that results in premature release of the nutrient core material during storage, for example, one approach that could be taken would be to suppress the water transport into the granule core. An alternative approach would be to prevent the transport of dissolved core nutrient solution out of the core. A third possible approach would be to combine both of the above-noted procedures by suppressing water transport into the core and preventing transport of dissolved nutrients out of the core. However, the most effective approach for avoiding water transport resulting in premature release of nutrient core materials would be to formulate the coatings of the CRF products in a manner such that the coatings actually cause xe2x80x9clock offxe2x80x9d of the nutrient core material.
Heretofore, it has been generally acknowledged that coating of nutrient core materials with too thick a coating layer or with a coating having overly effective barrier properties towards water transport and the like would result in CRF products exhibiting xe2x80x9clock offxe2x80x9d nutrient release characteristics. Such products have been considered to be highly undesirable since there has been no effective and/or cost efficient mechanism for releasing the nutrients at a desired time from the core of a product exhibiting such xe2x80x9clock offxe2x80x9d release characteristics. In fact, it has been believed previously that a coated fertilizer product that exhibits xe2x80x9clock-offxe2x80x9d necessarily would be agronomically ineffective as a result of the inability of the product to release sufficient amounts of nutrients during a given fertilization period. CRF products have been considered to suffer from xe2x80x9clock-offxe2x80x9d condition when less than 10 weight percent (wt %) of the nutrient core materials release from the CRF product after the product is exposed to moisture.
In published U.S. patent application Ser. No.2002/0004059, base-triggered release microcapsules are described wherein the microcapsules are formed of an amnioplast shell wall which breaks down or disintegrates relatively quickly under basis pH conditions to release an encapsulated substance, preferably, a liquid material such as a liquid pesticide. As described in this publication, when the microcapsules are not in a basic environment, they function as typical diffusion controlled release microcapsules, permitting release of the encapsulated substance into the surrounding area in a controlled manner which is determined by wall characteristics of the shell such as thickness, capsule size, permeability, etc. Thus, these microcapsules do not cause xe2x80x9clock offxe2x80x9d of the encapsulated liquid materials and effectively act as a controlled release product until they are placed in a basic environment at a pH of about 8-13 at which time the capsule wall is cleaved to xe2x80x9ctriggerxe2x80x9d or initiate breakdown of the capsule wall to enable complete release of the encapsulated liquid.
Thus, it has been recognized heretofore that it would be highly desirable to provide CRF products which exhibit delayed transport of water into contact with the nutrient core for a period of time specifically controlled by a user of the products. However, it has been a continuing problem in formulating such CRF products and there has been a long felt need for fertilizer products which effectively exhibit no premature release of nutrient core material during storage under moist/damp conditions such as are found in substrates such as wet growing media, soils and the like. Specifically, a need has existed for unique types of CRF products that: (i) essentially exhibit xe2x80x9clock offxe2x80x9d effects when stored in growing media so that no premature release of nutrients occurs, particularly, in wet growing media; and (ii) can be xe2x80x9ctriggeredxe2x80x9d to begin release of the nutrients at a particular time as determined by a user of the products. Such products can be characterized as being xe2x80x9ctriggered startxe2x80x9d or xe2x80x9cTSxe2x80x9d products and are referenced as such herein.
In this regard, it should be recognized that so-called xe2x80x9ctriggered startxe2x80x9d or TS products should not only display a delay of nutrient release but, also, should demonstrate initiation of nutrient release at a time under the control of and determined by a user of the products dependent upon application of a so-called xe2x80x9ctriggerxe2x80x9d composition by the user so that the nutrient release xe2x80x9clock offxe2x80x9d can be overcome at any time by applying the trigger composition. It should be further recognized that no particulate controlled release agricultural products have been known heretofore which could be classified as triggered start or TS products including, but not limited to, products wherein the water soluble core materials comprise insecticides, herbicides, fungicides, pheromones, biostimulants, growth regulators, animal repellents, insect repellents and the like in addition to fertilizers.
Accordingly, it is a principle object of the present invention to provide coated triggered start or TS products, especially fertilizer products as well as other products such as those having insecticides, herbicides, fungicides, pheromones, biostimulants, growth regulators, animal repellents, insect repellents and the like as the active constituent of the core materials.
It is a more specific object to provide coated controlled release products exhibiting xe2x80x9clock-offxe2x80x9d-type release characteristics whereby release of active constituents such as fertilizer nutrients and other water soluble core materials from the coated products is essentially completely suppressed or inhibited until release is initiated or triggered by application of a suitable trigger composition to the products at a time under the control of and in an amount determined by a user of the products.
A further object is to provide coated triggered start or TS products in which the coating layer causes less than 10 weight percent of the active constituents of the core material to release from the products after the products are exposed to moisture prior to the application of a trigger material such as a biological and/or chemical release agent to the coating layer.
Other objects of this invention are to provide processes for producing coated triggered start or TS products and for utilizing coated triggered start or TS products applied to a substrate such as a growing medium.
The foregoing and other objects of the invention are accomplished by providing a coated triggered start product and processes for producing and using such triggered start product. The triggered start product comprises a particulate core material having at least one water soluble active constituent such as a fertilizer, an insecticide, a herbicide, a fungicide, a pheromone, a biostimulant, a growth regulator, an animal repellent, an insect repellent and the like and mixtures thereof; and at least one coating layer applied on the particulate core material whereby the coating layer causes the product to exhibit xe2x80x9clock-offxe2x80x9d-type release characteristics in which the release of the active constituent(s) of the core material from the coated product is essentially completely suppressed until release is initiated by application of a trigger material to the coating layer. Coated triggered start products exhibit xe2x80x9clock-offxe2x80x9d-type release characteristics when less than 10 weight percent of the active constituent(s) of the core material releases from the product after the product is exposed to moisture prior to the application of the trigger material to the coating layer.